1. Field of the Invention
The present invention relates to a nozzle or a nozzle system for propellant driven inhalers for the administration of aerosol formulations into the lungs by inhalation.
2. Description of the Prior Art
In propellant driven inhalers, the active substances are stored together with the propellant in cartridge-like canisters. These canisters generally comprise an aluminium container sealed with a valve cup made of aluminium in which a valve is embedded. A canister of this kind can be inserted in the inhaler like a cartridge and is either left there permanently or replaced by a new cartridge after use.
Usually, the canister or container is formed from a casing made of aluminium, aluminium coated on the inside with an inert plastic, or stainless steel and the like. A single container usually has four different zones: the flat or concave inwardly domed base, a cylindrical belly region that merges at its upper third into a tapering neck region, and finally terminating in an edge region, e.g., a crimped edge, that defines the opening of the container.
Typically, these containers are of dimensions such that they can hold a volume of from about 5 to about 50 ml.
In the closed state the container is tightly sealed by the valve cup, usually after being filled or loaded with the pharmaceutical formulation and the propellant. For an example of a valve cup, reference is hereby made to GB 2324121, which is incorporated herein by reference in its entirety.
In the closed state of the canister, the valve cup crimps around the container at its edge at the opening. Generally, a seal seals off the valve cup from the container. The seal may be of annular or disk-shaped construction and consist of materials that are suitable for use in pharmaceutical formulations with fluorohydrocarbons as propellant. Examples include: thermoplastic materials, elastomers, neoprene, isobutylene, isoprene, butyl-rubber, Buna rubber, nitrile rubber, copolymers of ethylene and propylene, terpolymers of ethylene, propylene and a diene, such as butadiene for example, or fluorinate polymers. The preferred materials are ethylene/propylene-diene terpolymers (EPDM). Preferably, the valve cup is substantially planar or substantially defines a plane, which is preferably substantially perpendicular to the longitudinal axis of the canister.
The valve cup is penetrated by a valve that has a valve stem on its side facing the interior of the container and on the outside a nozzle for nebulizing the propellant-containing aerosol formulation. The valve is sealed off from the valve cup in the central opening by a seal. In the simplest case, the valve is cylindrical. The base end of this cylinder projects into the interior of the container, and the head end projects out of the container. The head end contains the nozzle opening. The base end has an inlet for introducing the liquid or gas into the interior of the container.
Valves of this kind have inside them other components, such as springs or valve members. The valve is opened by a vertical movement into the container counter to a spring. A spring counteracts this movement and causes the valve to close automatically after actuation.
When an aerosol formulation is nebulized into an aerosol by means of a propellant driven inhaler known from the prior art by using the adiabatic expansion of the propellant, the aerosol produced travels at high speed. This is due to the fact that the propellant has a high vapor pressure and, consequently, when the valve is opened, a correspondingly high pressure is released. These high speeds mean that a significant part of the aerosol produced is left suspended in the oro-pharyngeal cavity of the patient inhaling it and is not therefore available to the intended site of activity, the lungs.